Question

Number of atoms in 560 g $Fe$ is:

• A. Twice that of 70 g $N_2$
• B. Half that of 20 g $H_2$
• C. Both A and B
• D. None of the above

Answer 1

The correct option is C Both A and B

Let N be Avogadro's number.
The atomic/molar masses of $Fe,N_2$ and $H_2$ are 56 g/mol, 28 g/mol and 2 g/mol respectively.
560 g $Fe=\frac{560g}{56g/mol}=10$ mol $Fe=10N$ atoms.
70 g $N_2=\frac{70g}{28g/mol}=2.5$ moles $N_2=2\times 2.5N=5N$ atoms.
Twice of this corresponds to $2\times 5N=10N$.
20 g of $H_2=\frac{20g}{2g/mol}=10$ mole $H_2=2\times 10N=20N$ atoms.
Half of this $=0.5\times 20N=10N$ atoms.
Hence, both A and B are correct options.